The broad, long-term objective is to develop a collaborative effort between two clinical trials networks, the Pediatric Blood and Marrow Transplant Consortium (PBMTC) and the Children's Oncology Group (COG), in order to enhance the availability, safety, and efficacy of Pediatric blood and marrow transplantation performed by the PBMTC and COG, jointly optimize BMT protocol performance by the PBMTC and cancer treatment by the COG, and to advance the science and application of BMT through coordinated development of research concepts and collection of data between the PBMTC, the COG, and related networks in BMT. The specific aims include: 1. To expand COG's clinical trails infrastructure to enable an inter-operable clinical research network in pediatric BMT in conjunction with PBMTC. 2. To evaluate the performance of the infrastructure and inter-network informatics applications to actual inter-group clinical trials. 3. To develop standardized informatics tools that will allow for optimal data sharing of clinical research data from clinical trials between the COG/PBMTC and other networks.